The German regional centre of Heilbronn, neighbouring towns and townships, are increasingly adversely affected by car traffic. The city of Heilbronn and the surrounding district have therefore decided to jointly establish an urban transport system based on the 'Karlsruhe Model'. Barbara Wagner reports.

The Karlsruhe Model comprises solutions necessary to conform to the German National Railway Construction and Operation Regulations (EBO), to the Tram construction and Operation Regulations (BOSTrab) as well as complying with town planning desiderata.
This involves designing new line extensions and rerouting existing lines with a focus on creating system interfaces between the 15kV162/3Hzac full-fledged railway and the 750Vdc tram.
Adoption of this operating and transport system makes it possible to create a customer-accommodating and relatively inexpensive regional railway network in smaller, densely populated areas.
For the City of Heilbronn this has meant sharing existing and using abandoned lines of the DB AG in accordance with the Railway Construction and Operation Regulations, as well as designing a new tram route through the centre of Heilbronn planned under provisions of the Tram Construction and Operation Regulations.
Operations will be assured by dual-system railcars as used in Karlsruhe. Trains from Baden-Baden and Karlsruhe will travel into the centre of Heilbronn.
The city centre loop begins at the main station, where it leaves the German Rail network and runs on two tracks to Friedensplatz (about 1.6kilometres long with four stops), where it ends for the time being. A stop at the station plaza will interface with urban and regional bus services.
Tracks in front of the station have 15kV162/3Hzac overhead power supply although they are located within the public transport domain. The system interchange, switching to 750Vdc tram current, takes place in the next section on a special sub grade.

One of the main technical challenges of this project was the design of the power supply within a dense city complex. A rectifier station had to be designed for the complete power supply within the first 1600metres of phase one of the project.
Within the Heilbronn city centre there was no adequate position available for a containerised system. Therefore, an underground rectifier station was placed at the station Harmonie.
The main components of the rectifier station consists of two rectifier units each with 2MW capacity as well as three track feeder cells and one bypass cell. Additional technical fixed installations for controlling the voltage supply were integrated.
The feeder and return conductor arrangement together with the above ground cable distributor were placed externally. The substation is remote controlled by the network control station of the power supplier ZEAG.
This type of system integration and the utilisation of confined areas has proven itself to be highly advantageous for passenger comfort and has therefore contributed to making the city centre more attractive. It has thereby become an example for other cities considering possible development options.

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Barbara Wagner is with DE-Consult (Deutsche Eisenbahn-Consulting GmbH), Karlsruhe, Germany. www.de-consult.de